Hyaluronic acid is linear polymeric polysaccharide in which β-D-N-acetylglucosamine and β-D-glucuronic acid alternatively bind to each other. Showing excellent biocompatibility and viscoelasticity, the hyaluronic acid is increasingly applied to medical uses. As one of the uses, Patent Literature 1 discloses the use of hyaluronic acid crosslinked as a viscosity replenisher for knee osteoarthritis.